The carbostyril derivatives (1) of formula (1) or salts thereof and the process for the preparation thereof are disclosed in JP-63-20235-B and JP-55-35019-A. And it is known that the carbostyril derivatives (1) have platelet aggregation inhibition action, phosphodiesterase (PDE) inhibition action, antiulcer, hypotensive action and antiphlogistic action, and are useful as an antithrombotic agent, a drug for improving cerebral circulation, an antiinflammatory agent, an antiulcer drug, an antihypertensive drug, an antiasthmatic drug, a phosphodiesterase inhibitor, etc. In addition, JP-2006-518732-A (PTEN INHIBITOR OR MAXI-K CHANNELS OPENER) discloses that the carbostyril derivatives (1) are useful as a medicament for treating anxiety, depression, etc.
Schizophrenia mainly affects people at the period of puberty or adolescence, which is basically caused by disturbance of ego, thought disorder, etc. And schizophrenia is categorized as a chronic psychiatric disorder which gradually becomes severe as positive symptom including hallucination and delusion arises repeatedly.
With the change of social lifestyle and the advance of aging of society, the number of patients suffering from neuropsychiatric disease tends to increase on the whole. For example, schizophrenia is apt to affect about 1% of all the population without the relation to races or areas, which is a neuropsychiatric disease mainly affecting people at the young period from puberty to their twenties. The hospitalized patients suffering from schizophrenia occupy about 15% of the total beds of hospitals in Japan, hence the disease is a big social problem from the viewpoint of medical economy. The conditions of schizophrenia include a positive symptom such as hallucination and delusion, and a negative symptom such as apathy, hypobulia and social withdrawal. The treatment of schizophrenia requires appropriate medicaments, which include phenothiazines, butyrophenones, benzamide compounds, iminodibenzyl compounds, thiepins, indole compounds and serotonin/dopamine receptor blockers as a conventional treatment drug. However, a novel and more effective medicament for treating schizophrenia is still desired in Japan and other countries since the current medicaments are not sufficiently effective.